var f = new Promise(function(resolve, reject){
    setTimeout(function(){
        resolve('hello');
    },10);
}).then(value1=>{
    return new Promise(function(resolve, reject){
        setTimeout(function(){
            resolve(value1+' lagou');
        },10);
    });
}).then(value2=>{
    setTimeout(function(){
        console.log(value2+' I LOVE U');
    },10);
});

